A senior U.S. official says the United States sees no need "at all" for Iran to build additional nuclear power plants.

Assistant Secretary of State Nicholas Burns made the remark in an interview Friday with the Reuters news service. He was responding to comments today by Iran's ambassador to Russia, Gholamreza Ansari, that Tehran has started building a second nuclear plant and is considering ways to fuel the facility.

Burns also told Reuters that Iran's test rocket launch on Monday -- and media reports that Iran is testing advanced centrifuges to enrich uranium are -- in his words -- "deeply disturbing."

He said the proper response to such developments would be passage of a third U.N. sanctions resolution on Iran.

Iran says the rocket it tested will be used to launch a new satellite in space.

The U.N. Security Council has already imposed two sets of sanctions on Iran for its failure to suspend uranium enrichment -- a process that can be used to make nuclear weapons.

Officials from Germany and the five permanent members of the Council, the U.S., Britain, France, Russia and China, recently agreed on the text of a resolution that will impose a third round of sanctions against Iran.

Iran has been building its first nuclear power plant near the southern city of Bushehr. Officials say Russia has delivered enough nuclear fuel to run that plant, and that the facility will open later this year.

The United States and its Western allies accuse Iran of developing technology to produce atomic weapons. Tehran denies the charge.